The new Kerala Municipality Building (Amendment) Rules 2004 which came into effect yesterday means an additional expense of Rs 1,000 to Rs 12,000 for new houses and upto Rs 1 lakh for commercial establishments to ensure rooftop rainwater harvesting system on the buildings. The basic method of fixing pipes and sand filters to recharge the water to wells is prescribed for small households and the expense for this will fall below Rs 1000 and for the houses which use around 1000 litres of water every day, a bigger tank with pumping facilities needs to be provided at an estimated cost of Rs 10,000 to Rs 12,000.